Multilayer Pressure-sensitive adhesive construction

ABSTRACT

The present invention is directed toward a multilayer, pressure-sensitive adhesive construction wherein one layer is formed of a first adhesive composition having a first glass transition temperature, and at least a second layer is formed of a second adhesive composition having a second glass transition temperature. The first glass transition temperature differs from the second glass transition temperature by from about 10° C. to about 50° C.

FIELD OF THE INVENTION

The present invention relates to pressure-sensitive adhesiveconstructions, and more particularly, to multilayer pressure-sensitiveadhesive constructions which exhibit both good adhesion and goodconvertibility.

BACKGROUND OF THE INVENTION

A conventional pressure-sensitive adhesive (PSA) label constructioncomprises a laminate of a facestock, a pressure-sensitive adhesivelayer, and a coated release liner. The facestock may comprise any of avariety of materials, but is typically formed from paper or plasticfilms. The release liner provides a backing from which the facestock andthe pressure-sensitive adhesive are peeled away just prior to labelapplication. The surface of the release liner often consists of papercoated with a release layer of silicone.

Pressure-sensitive adhesive tape and label constructions are usuallymanufactured as a continuous roll in various widths, and are thenprocessed to form finished product consisting of commercially usefullabels or tape rolls. Such processing, known as converting, ofteninvolves cutting all or part of the bulk laminate roll. For example, onecommon converting operation in label manufacture is die cutting andmatrix stripping, which involves precision cutting through the facestockand adhesive layers up to but not through the release surface, therebycutting outlines of the labels, and then pulling away the surroundingmatrix to leave only the individual labels on the release liner. Otherconverting operations may include butt cutting, guillotining, holepunching, slitting, and printing.

The cost of converting the bulk laminate PSA construction into thefinished product depends in large part on the speed in which theconverting processes can be carried out. The faster the PSA constructioncan be converted, the lower the cost of the finished product. Modernconverting presses are designed to be operated at speeds of as high as800 feet per minute or greater, and it is desirable to manufacture PSAconstructions compatible with this converting speed.

It has been discovered that all layers of the laminate have some effecton converting speed, and much work has been directed at optimizing thefacestock and release surfaces for faster converting. For example,increasing matrix stripping speed generally increases stripping force,which often results in matrix breaks which force press shutdown. Thisproblem may be avoided by the use of higher strength facestocks, whichconvert better than low strength facestocks at a variety of convertingspeeds.

The adhesive layer, however, has been the greatest limiting factor withrespect to the speed of converting bulk laminates into finished product.It is desirable to have an adhesive layer with good flow properties thatcan adhere to a wide variety of substrates. However, adhesivecompositions which are formulated to have these properties do not alwaysconvert well, oftentimes sticking to the cutting dies, smearing on thematrix and label edges, and interfering with the precision cutting, orotherwise slowing down the converting process.

In addition, adhesive layers may also impact the matrix strippingoperations which follow die cutting, causing breaks in the matrix if theconverting press is run at too high a speed. To avoid these matrixbreaks, press operators are often forced to slow the converting pressesto well below the optimal operating speed.

Thus, it is desirable to provide pressure-sensitive adhesiveconstructions which feature adhesive layers which show good adhesion toa wide variety of substrates of varying roughness, and which are alsocompatible with optimal converting performance.

SUMMARY OF THE INVENTION

The present invention is directed toward pressure-sensitive adhesiveconstructions which show good adhesion to a wide variety of substrates,and which also convert well.

In one aspect of the present invention, there is provided apressure-sensitive adhesive construction with a facestock. A firstadhesive layer is on the facestock. The first adhesive layer comprises afirst adhesive composition with a first glass transition temperature.The first adhesive composition may be either an acrylic based or arubber-based adhesive and may include a first organic additive.

A second adhesive layer is on the first adhesive layer. The secondadhesive layer comprises a second adhesive composition with a secondglass transition temperature which is lower than the first glasstransition temperature. The second adhesive composition may be either anacrylic based or a rubber-based pressure-sensitive adhesive and mayinclude a second organic additive. A release liner may be on the secondadhesive layer

Preferably, the first glass transition temperature is about 10° C. toabout 50° C. higher than the second glass transition temperature. Morepreferably, the first glass transition temperature is about 15° C. toabout 35° C. higher than the second glass transition temperature.

If a rubber-based adhesive layer is present in the first and/or secondlayer, it may contain polymeric components selected from a groupconsisting of block copolymers of styrene-butadiene-styrene,styrene-isoprene-styrene, styrene-butadiene, styrene-isoprene,multibranched styrene-butadiene, and multibranched styrene isoprene,individually, or in combinations thereof. If an acrylic based adhesivecomposition is present in the first or second adhesive layer, it mayconsist in part of polymers formed from the polymerization of at leastone alkyl acrylate monomer, where the alkyl group contains from aboutfour to about twelve carbon atoms, in an amount from about 35% to about95% by weight of the polymer.

When rubber-based adhesive composition are used, the organic additive inthe adhesive composition includes a tackifier present in a concentrationby weight of about 40-90%. Moreover, the organic additive might alsoinclude a plasticizer, present in the first adhesive composition and/orsecond adhesive composition in concentration of about 1-30% by weight.

In another aspect of the present invention, there is provided apressure-sensitive adhesive construction with a facestock. A first layeris on the facestock. The first layer has a first polymeric compositionwith a first glass transition temperature. The first polymericcomposition also has a first storage modulus, and a first tangent delta.A second layer is on the first layer. The second layer has a secondpolymeric composition with a second glass transition temperature. Thesecond polymeric composition is a pressure-sensitive adhesivecomposition.

The first layer has mechanical loss such that it contributes to the peelforce. The first layer also has a high storage modulus at die-cuttingfrequency so as to prevent smear. Thus, in a preferred embodiment ofthis aspect of the invention, the first storage modulus at a frequencyof 10⁴ radians per second at 20° C. is greater than about 3×10⁸dynes/cm², and the first tangent delta at 10² radians per second at 20°C. is greater than about 0.5. In this embodiment, the first layer maycomprise a pressure-sensitive adhesive layer, or it may comprise anadhesive layer which does not exhibit pressure-sensitive adhesiveproperties.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a conventional pressure-sensitiveadhesive construction.

FIG. 2 is a cross-sectional view of a pressure-sensitive adhesiveconstruction of the present invention.

FIG. 3 is a plot of the loss modulus, the storage modulus, and tangentdelta of adhesive Formulation 2 in Table I as a function of temperatureat 10 radians per second.

FIG. 4 is a plot of the loss modulus, the storage modulus, and tangentdelta of adhesive Formulation 1 in Table I as a function of temperatureat 10 radians per second.

FIG. 5 is a schematic diagram of a dual die used to apply the adhesiveformulations of the present invention.

FIG. 6 is a cross-sectional schematic view showing the lip structure ofthe dual die of FIG. 5 as it is applying two layers of adhesive.

FIG. 7 is a cross-sectional schematic showing an angled lip structure ofthe dual die as it is applying two layers of adhesive.

FIG. 8 is a cross-sectional schematic of a dual die featuring a beveledlip structure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is directed to multilayer adhesive constructionsshowing improved convertibility as well as good adhesion and aging.

In one embodiment of the present invention, this is achieved byproviding a multilayer pressure-sensitive adhesive construction whichcomprises two or more adhesive layers, at least one of which is apressure-sensitive adhesive layer, and where at least one of the layershas an adhesive composition with a glass transition temperature thatdiffers from the glass transition temperature of an adhesive compositionin a different layer. In this embodiment, it is preferred that theadhesive layer nearest the facestock contain the adhesive compositionwith the highest glass transition temperature. The adhesive layernearest the release layer has the adhesive composition with the lowerglass transition temperature, and may be selected for its desirableadherent properties. It has been discovered that multilayer adhesiveconstructions of this design, which feature at least two adhesive layerswith differing glass transition temperatures, show markedly improvedconvertibility relative to conventional pressure-sensitive adhesiveconstructions.

As used herein, the term "glass transition temperature" (Tg) refers tothe temperature at which an adhesive composition, which may includepolymers, resins, and oils, and other ingredients, changes from a glassyto a rubbery state. For block copolymer based adhesives (SIS, SBS, SI,SB, SEBS, or other block copolymers with endblocks of polystyrene), theTg reflects only the midblock of the elastomer components of theadhesive composition. The term "native glass transition temperature," asused herein, refers to the glass transition temperature of a particularcomponent of the adhesive composition, such as a polymer, as thatcomponent exists in its pure form.

In another embodiment of the present invention, a multilayerpressure-sensitive adhesive construction with improved convertabilityand good adhesion is achieved by providing a multilayer adhesiveconstruction with a first layer, wherein the first layer has a storagemodulus which, at a frequency of 10⁴ radians per second at 20° C., isgreater than about 3×10⁸ dynes/cm², and a tangent delta, which at 10²radians per second and 20° C., is greater than about 0.5. A secondadhesive layer comprising a pressure-sensitive adhesive may be incontact with the first layer, thereby providing an adhesive layer whichshows good adhesion to a wide variety of substrates. Multilayer adhesiveconstructions of this design also exhibit good convertability and goodadhesion to a variety of substrates of varying surface roughness.

Referring to FIG. 1, for comparison purposes, there is depicted aconventional pressure-sensitive adhesive construction. Construction 10features a facestock 12, a pressure-sensitive adhesive layer 14 ofuniform composition in contact with the facestock 12, and a releaselayer 16, having a release surface thereon, in contact with thepressure-sensitive adhesive layer 14.

Although the present invention will be described in the context of aconstruction having a release layer, the present invention is equallyapplicable in the context of a construction such as for the productionof tape in which the release layer is omitted and a release surface isprovided on the opposite side of the facestock from the adhesive. It iscontemplated that tape constructions may benefit from the advantages ofthe present invention during various converting operations involvingcutting of the bulk tape roll, such as slitting.

In addition, although the present invention may be described in thecontext of having two pressure-sensitive adhesive layers, it is equallyapplicable to a multilayer adhesive construction where only the adhesivelayer nearest the release layer is a pressure-sensitive adhesive, andwherein the other layers may or may not be an inherently tacky adhesivelayer, as described more fully below. Thus, the term "adhesive layer,"and "adhesive composition," as used herein, are meant only to refer tolayers, or the adhesive compositions in those layers, with at least thatminimal degree of tack required to adhere to a particular facestocksubstrate of an adhesive construction. An "adhesive layer" or "adhesivecomposition" may include, but does not necessarily include,"pressure-sensitive adhesive layers" or "pressure-sensitive adhesives,"which possess substantially greater tack than that minimal degree oftack needed to adhere to the facestock, and which adhere well to avariety of substrates on contact.

Referring to FIG. 2, there is depicted one embodiment of the multilayerpressure-sensitive adhesive construction of the present invention whichfeatures two pressure-sensitive adhesive layers. Multilayerpressure-sensitive adhesive construction 20 is comprised of a facestock22, a first pressure-sensitive adhesive layer 24 in contact with thefacestock 22, a second pressure-sensitive adhesive layer 26 in contactwith the first pressure-sensitive adhesive layer 24, and a release layer28 in contact with the second pressure-sensitive adhesive layer 26.Pressure-sensitive adhesive layers 24 and 26 each have one or morepolymerized components, as well as other components discussed below,which combine to form an adhesive composition with at least one glasstransition temperature. The glass transition temperatures of theadhesive compositions of the respective adhesive layers differs.

As can be readily seen from comparison of FIGS. 1 and 2,pressure-sensitive adhesive constructions of the present inventiondiffer from conventional pressure-sensitive adhesive constructions, inaddition to ways described more fully below, by having two layers 24 and26. In one embodiment, described above, layers 24 and 26 are both formedof inherently tacky pressure-sensitive adhesive compositions, and thuscomprise pressure-sensitive adhesive layers. In an alternate embodiment,described in more detail below, layer 24 is formed of a polymericcomposition which is not inherently tacky, and does not exhibitpressure-sensitive adhesive properties, thereby forming an adhesivelayer 26 which is not a pressure-sensitive adhesive layer.

In addition, although not depicted, it is contemplated that theteachings of the present invention are applicable to create multilayerpressure-sensitive adhesive constructions which feature three or morelayers, where one or more layers may comprise a pressure-sensitiveadhesive, and which show the improved convertibility and aging ofconstructions of the present invention.

In all embodiments of the present invention, layers 24 and 26 arecomprised of polymeric compositions. Various other organic and inorganicsubstances may be added to the polymeric compositions as may be desiredto alter the properties of the layers. For example, additives may beselected to enhance the adhesive properties of a particular layer, asdescribed more fully below.

The polymeric components of layers 24 and 26 may consist of any of avariety of polymers which are known to be useful in the formation ofadhesive compositions, such as natural or synthetic elastomers, oracrylic based adhesive compositions. For example, adhesive layers 24 and26 may both consist of compositions including elastomeric polymers, orthey may both consist of compositions including acrylic polymers.Alternately, either layer 24 or 26 may consist of a compositionincluding an elastomeric polymer, with the other layer being acomposition including an acrylic polymer. Layers 24 and 26 may be formedwith identical polymer components or different polymer components.

In addition, although layer 26 should comprise a pressure-sensitiveadhesive, and thus should be formed from an adhesive composition whichimparts pressure sensitive properties, layer 24 may or may not be formedof a pressure-sensitive adhesive composition. In the preferredembodiment, layer 24 only need possess sufficient tack to adhere tofacestock 22 when laminated at room temperature or elevated temperature.However, as can be appreciated by one of skill in the art, the polymericcompositions in layers 24 and 26 must be sufficiently compatible toadhere to one another strongly enough to prevent separation of layers 24and 26 when the facestock 22 and layers 24 and 26 are removed from therelease layer 28, as for example, when a label construction is peeledfrom its backing.

In one embodiment, either layer 24 or 26, or both layers 24 and 26, maybe formed from an acrylic based polymer. It is contemplated that anyacrylic based polymer capable of forming an adhesive layer withsufficient tack to adhere to the facestock 22 may function in thepresent invention. In addition, with respect to layer 24, and layer 26in certain embodiments, presently preferred acrylic polymers for thepressure-sensitive adhesive layers include those formed frompolymerization of at least one alkyl acrylate monomer containing fromabout 4 to about 12 carbon atoms in the alkyl group, and present in anamount from about 35-95% by weight of the polymer or copolymer, asdisclosed in U.S. Pat. No. 5,264,532 issued to Bernard. Optionally, theacrylic based pressure-sensitive adhesive might be formed from a singlepolymeric species.

Advantageously, the glass transition temperature of an adhesive layercomprising acrylic polymers can be varied by adjusting the amount ofpolar, or "hard monomers," in the copolymer, as taught by U.S. Pat. No.5,264,532, incorporated herein by reference. The greater the percentageby weight of hard monomers in an acrylic copolymer, the higher the glasstransition temperature. Hard monomers contemplated useful for thepresent invention include vinyl esters, carboxylic acids, andmethacrylates, in concentrations by weight ranging from about zero toabout thirty-five percent by weight of the polymer.

In another embodiment, layers 24 and 26 each include at least oneunsaturated elastomeric polymer. The elastomeric polymers used arepreferably based on di-block and tri-block copolymers ofstyrene/butadiene and styrene/isoprene. For example,styrene-butadiene-styrene, styrene-isoprene-styrene, styrene-butadiene,and styrene-isoprene block copolymers, such as the Kraton polymersmanufactured and sold by Shell Chemical Company, of Houston, Tex. andthe Solprene polymers manufactured and sold by Housemex, Inc., locatedin Houston, Tex., are suitable for use in the instant invention.Multibranched styrene-butadiene and multibranched styrene-isoprene, ofthe formula (SB)_(x) and (SI)_(x), respectively, where x is greater than2, may also be used.

Co-blends of Kraton RP 6419, a styrene-isoprene-styrene block copolymer,and Solprene 1205, a styrene-butadiene block copolymer, have proven tobe particularly suited for the polymeric compositions of the respectivelayers. When a co-blended elastomeric polymer composition is used, morethan one glass transition temperature may be observed, as taught by U.S.Pat. No. 5,290,842, issued to Sasaki, et al., incorporated herein byreference. In such a case the temperature corresponding to the majorpeak, as observed on a plot of tangent delta as a function oftemperature, is the important glass transition temperature for purposesof the present invention.

The polymeric compositions of the respective layers 24 and 26 may bothfunction as pressure-sensitive adhesives, although this is not requiredfor those layers not in contact with the release layer. However,unsaturated elastomeric polymers normally do not function aspressure-sensitive adhesives by themselves. Pressure sensitiveproperties are imparted to compositions containing unsaturatedelastomeric polymers by the addition of other organic molecules known astackifiers. Tackifiers, are generally hydrocarbon molecules, woodresins, pall resins, and the like, which when present in concentrationsranging from about 40% to about 90% by weight of the total adhesivecomposition, more preferably from about 45% to about 85% by weight,impart pressure-sensitive adhesive characteristics to the elastomericpolymer adhesive formulation. Compositions containing less than about40% by weight of tackifier additive do not generally show sufficient"quickstick," or initial adhesion, to function as a pressure-sensitiveadhesive, and therefore are not inherently tacky. Compositions with toohigh a concentration of tackifying additive, on the other hand,generally show too little cohesive strength to work properly in mostintended use applications of constructions made in accordance with theinstant invention.

Tackifier additives are well known in the art, and may be used toincrease the glass transition temperature of the unsaturated elastomericpolymer adhesive composition, in proportion to increasing weightconcentration of the tackifier. Thus, in addition to their ability toimpart pressure-sensitive adhesive properties to the compositions of theinstant invention, tackifiers may also be selected to optimize thedifference of the glass transition temperatures between the adhesivecompositions in different layers. For example, with reference to FIG. 2,the glass transition temperature of the adhesive composition in adhesivelayer 24 could be increased by increasing the concentration by weight ofa tackifying additive in layer 24. Similarly, the glass transitiontemperature of the adhesive composition in adhesive layer 26 could bedecreased by decreasing the concentration by weight of tackifyingadditive in layer 26.

Tackifier additives useful for practicing the present invention arethose which impart pressure-sensitive adhesive properties to theelastomeric polymer compositions, and which also serve to increase theglass transition temperature of the adhesive compositions. It iscontemplated that any tackifier known by those of skill in the art to becompatible with elastomeric polymer compositions may be used with thepresent embodiment of the invention. One such tackifier, found usefulfor the Solprene 1205/Kraton RP 6419 blends discussed previously, isWingtak 10, a synthetic polyterpene resin which is liquid at roomtemperature, and sold by the Goodyear Tire and Rubber Company of Akron,Ohio. Other suitable tackifying additives may include Escorez 1310 andEscorez 2596, both manufactured by Exxon of Irving, Tex. Of course, ascan be appreciated by those of skill in the art, a variety of differenttackifying additives may be used to practice the present invention.

In contrast to tackifiers, plasticizers are organic molecules, whichform liquids at room temperature, and which are known to decrease theglass transition temperature of an adhesive composition containingelastomeric polymers. Thus, plasticizers may be used in the instantinvention, alone or in combination with tackifiers, to alter the glasstransition temperature of a particular adhesive composition in one ofthe adhesive layers. One plasticizer found useful for practicing thepresent invention is Shellflex 371, a naphthenic processing oilavailable from Shell Oil Company of Houston, Tex. However, anyplasticizer known by those of skill in the art to be compatible withelastomeric polymer compositions may be used to practice the presentinvention.

Many liquid tackifiers or plasticizers which might be used withelastomeric polymers are composed of small organic molecules which arecapable of migrating between adjacent adhesive layers. Migration isespecially likely to occur if the liquid concentration of tackifiers andplasticizers in one elastomeric polymer adhesive layer greatly exceedsthat present in an adjacent elastomeric polymer adhesive layer.Migration of these species is undesirable, as it leads to loss ofadhesion over time, otherwise known as poor "aging" of the adhesivelayer. To minimize the chances for migration to occur, it is preferredthat the weight ratio of the sum of elastomeric polymer to the sum ofliquid tackifiers and plasticizers in a particular layer, defined hereinas the "polymer to liquid tackifier and plasticizer ratio," be roughlyequal between adjacent layers.

In addition to tackifiers and plasticizers, other additives may be usedin the adhesive compositions to impart desired properties. For example,anti-oxidants may be used to protect the polymers from oxidativedegradation. Suitable anti-oxidants useful in practicing the presentinvention include Irgafos 168 and Irganox 565, available fromCiba-Geigy, located in Hawthorne, N.Y.

Various cutting agents, such as waxes and surfactants, as taught by U.S.Pat. No. 5,322,876, issued to Sasaki, may also be added to the adhesivecompositions of the present invention. For example, Pluronic F108, ablock copolymer surfactant having polyethylene-oxide andpolypropylene-oxide blocks, and manufactured by BASF, has been founduseful in practicing the present invention. Polyethylene glycol waxes,such as Carbowax 1450 manufactured by Union Carbide, located in Danbury,Conn., may also be used.

Filler components such as Camel Wite, which consists of calciumcarbonate, and is available from Genstar Stone Products Co., located inHunt Valley, Mo., may also be used in the adhesive compositions of thepresent invention.

Representative formulations of adhesive compositions useful inpracticing the present invention are set forth in Table I. All valueslisted are parts by weight.

                  TABLE I                                                         ______________________________________                                                Formulation 1                                                                           Formulation 2                                                                            Formulation 3                                            (ppw)     (ppw)      (ppw)                                            ______________________________________                                        Kraton RP 6419                                                                          20          13         --                                           Solprene 1205                                                                           10          7          10                                           Escorez 2596                                                                            46          64         43.3                                         Wingtack 10                                                                             12          8          23.5                                         Shellflex 371                                                                           12          8          --                                           Kraton 1107                      23.2                                         Camel Wite                                                                              8.5         8.5        3                                            Irgafos 168                                                                             0.6         0.6        0.6                                          Irganox 565                                                                             0.3         0.3        0.3                                          Pluronic F108                                                                           --          --         3                                            Carbowax 1450                                                                           --          --         3                                            Total     109.4       109.4      109.9                                        ______________________________________                                    

Referring to FIG. 2, it is important to the functioning of the presentinvention that the glass transition temperatures of the adhesivecompositions in adhesive layers 24 and 26 differ. Preferably, the glasstransition temperatures should differ by about ten to about fiftydegrees Celsius. More preferably, the glass transition temperaturesshould differ by about ten to about thirty degrees Celsius. In a mostpreferred embodiment, the glass transition temperatures differ by aboutfifteen to about twenty-five degrees Celsius.

In a one embodiment, the adhesive layer containing the adhesivecomposition with the higher glass transition temperature is in contactwith the facestock 22, and the adhesive composition with the lower glasstransition temperature is in contact with the release layer 28. It hasbeen discovered that pressure-sensitive adhesive constructions embodyingthis design show improved converting properties, as will be discussedbelow.

For purposes of the present invention, it is the difference between theglass transition temperatures of the adhesive compositions in theadhesive layers that appears to reflect one characteristic important tothe functioning of the present invention. In an optimal embodiment ofthe present invention, the difference in the glass transitiontemperature between the two layers is such that the layer in contactwith the facestock has at least a sufficient amount of tack to adhere tothe facestock, while the adhesive layer nearest the release layer isinherently tacky. The degree of tack possessed by a particular adhesivelayer is dependent in large part on the glass transition temperature ofthe adhesive composition of that layer. If the glass transitiontemperature is too high, the composition will fail to function as anadhesive. In contrast, if the glass transition temperature is too low,the adhesive composition may flow too readily, which diminishesconverting performance. Various components of the adhesive compositionhave native glass transition temperatures, which contribute to theobserved glass transition temperature of the adhesive composition as awhole. These components include the polymers, tackifiers, plasticizers,fillers, and various other additives known to those of skill in the art.

In addition, if a particular adhesive is to function as apressure-sensitive adhesive, as is required for the adhesive layernearest the release surface, the adhesive composition should have aglass transition temperature of at least about 5 degrees to about 70degrees Celsius below the contemplated use application temperature, morepreferably from about 10 degrees to about 50 degrees below thecontemplated use application temperature.

Another important characteristic to the functioning of the presentinvention is the storage modulus (G'), which is a measure of the energystored and recovered in a viscoelastic adhesive composition. Adhesivecompositions with a sufficiently high storage modulus for a given amountof force exhibit less deformation, and are therefore less likely toadhere to cutting blades or dies used in the converting process. In oneembodiment of the present invention, it is preferred that the layer withthe higher storage modulus be in contact with the facestock 22. Thelayer with the lower storage modulus is in contact with the releaselayer 28. In this embodiment it is preferred that the layer in contactwith the facestock have a storage modulus, at 10⁴ radians per second and20° C., within the range of from about 1×10⁸ dynes/cm² to about 5×10⁹dynes/cm², more preferably in the range from about 3×10⁸ dynes/cm² toabout 1×10⁹ dynes/cm², and most preferably within the range from about3×10⁸ dynes/cm² to about 8×10⁸ dynes/cm².

The glass transition temperature and storage modulus of adhesivecompositions used in the present invention can be determined by variousmethods known to those of skill in the art. Because of the viscoelasticnature of the adhesive compositions, the Tg value will be dependent onthe type and rate of these methods. One such method is to plot thetangent delta, which is the ratio of the loss modulus (G") to thestorage modulus (G'), as a function of temperature. The temperature atwhich the tangent delta peak occurs, at a frequency of 10 radians persecond, represents the glass transition temperature. The loss modulus(G") is a measure of the energy dissipated as heat or sound per cycle ofsinusoidal deformation, when different systems are compared at the samestrain amplitude. In addition, for pressure-sensitive adhesives, lossmodulus can be correlated to the amount of energy dissipated in peelingthe viscoelastic polymeric material from a substrate.

Tangent delta (tan δ) is measured by placing an approximately 1.5-2 mmthick sample of an adhesive composition between two 8 mm parallel platesof a Rheometrics instrument (model RMS-800 manufactured and sold byRheometrics, Inc., Piscataway, N.J.), and oscillating the platesrelative to one another at 10 radians per second. The parallel platesare heated at a rate of 1° C. per minute during the test. Measurementsof the storage modulus, loss modulus, and tangent delta are made at 3°C. intervals. In addition, either the loss modulus, or storage modulus,may be measured individually using a similar protocol, but differentfrequencies, as is known by those of skill in the art.

FIG. 3 is a plot of tangent delta as a function of temperature forFormulation 2 as disclosed in Table I. The glass transition temperaturecorresponds to the temperature at which the tangent delta peak occurs at10 radians per second, and is approximately 34 degrees Celsius.

FIG. 4 is a plot of the tangent delta as a function of temperature forFormulation 1 as disclosed in Table I. The glass transition temperaturefor this composition correspond to the temperature at which the tangentdelta peak occurs at 10 radians per second, and is about 10.7 degreesCelsius.

The glass transition temperatures of Formulations 1-2 of Table I, aswell as the storage modulus and tangent delta at 20° C. and at variousfrequencies, as determined using the Rheometrics instrument as discussedabove, are set forth below in Table II.

                                      TABLE II                                    __________________________________________________________________________           G'          G'          G'                                                    10.sup.2 radians/s                                                                  tan δ                                                                         10.sup.4 radians/s                                                                  tan δ                                                                         10.sup.5 radians/s                                                                  tan δ                                                                         Tg                                        dynes/cm.sup.2                                                                      10.sup.2 radians/s                                                                  dynes/cm.sup.2                                                                      10.sup.4 radians/s                                                                  dynes/cm.sup.2                                                                      10.sup.5 radians/s                                                                  °C.                         __________________________________________________________________________    Formulation 1                                                                        2.7 × 10.sup.6                                                                1.8   7.3 × 10.sup.7                                                                0.9   2.3 × 10.sup.8                                                                0.58  10.7                               Formulation 2                                                                        4.5 × 10.sup.7                                                                1.5   4.2 × 10.sup.8                                                                0.5   7.9 × 10.sup.8                                                                0.35  34                                 __________________________________________________________________________

Facestock 22, as depicted in FIG. 2, may comprise any of a variety ofmaterials known by those of skill in the art to be suitable as afacestock material. For example, facestock 22 may be composed of suchmaterials as paper, polyester, or other polymeric materials suitable forfacestock use such as polyethylene or polypropylene. The onlyrequirement for facestock 22 is that it be capable of forming somedegree of adhesive bond to adhesive layer 24, preferably by having layer24 adhere to the material selected as the facestock.

Similarly, release layer 28 may consist of any of a variety of materialsknown to those of skill in the art. In one preferred embodiment, usefulfor label manufacture, release layer 28 comprises a silicone coatedpaper substance.

The thickness of the adhesive layers 24 and 26 is typicallycharacterized in terms of the number of grams of adhesive compositionapplied per meter squared of the surface it is applied on. Generally, acoating weight of about 25 g/m² is roughly equal to a thickness of about1/1000 of an inch, although this may vary considerably depending on thedensity and type of adhesive used.

The present invention will work when the individual coat weight in eachof adhesive layer 24 and 26 is enough to form a discrete identifiablelayer. The total coat weight, defined as the sum of the coat weights ofadhesive layers 24 and 26, may vary from 15 g/m² to 125 g/m².

In single layer adhesive constructions using a rubber-based adhesivelayer, it has been discovered that convertability decreases inproportion to increasing coat weight of the adhesive layer. In theserubber-based systems, convertability decreases dramatically when theadhesive layer is coated at a weight of greater than 25 g/m². Therefore,in the preferred embodiment of the present invention, the sum of the twocoat weights of adhesive layers 24 and 26 ranges from about 15 g/m² toless than about 30 g/m², more preferably to less than about 25 g/m², andmost preferably to about 20 g/m².

Within the most preferred total coat weight of about 20 g/m², therespective coat weights of individual adhesive layers 24 and 26 may varyconsiderably. For example, the adhesive layer 24 nearest the facestockmay have a coat weight range of from about 5 g/m² to about 15 g/m².Similarly, the adhesive layer 26 furthest from the facestock may alsohave a coat weight range of from about 5 g/m² to about 15 g/m². Setforth in Table III are Examples 1-10, which utilize the adhesiveFormulations disclosed in Table I, and demonstrate a variety of coatweight ranges that the individual layers might comprise in nonlimitingexemplary embodiments of the present invention. As used in Table III,"Upper Adhesive Layer" refers to the layer nearest the facestock and"Lower Adhesive Layer" refers to the layer nearest the release liner.

Set forth in Table IV are adhesive data for Examples 1-10 of Table III.Looptack was determined by forming an 8" loop of a 1" wide sample,mounting the loop in the jaws of an Instron tester, and then moving theloop against a test surface at 12" per minute, and after a 1"×3" areawas covered, removing the loop at 12" per minute. The force recorded wasreported as looptack.

This data demonstrates that multilayer constructions of nonlimitingexemplary embodiments of the present invention show good adhesion to avariety of substrates. In addition, although not shown, it has also beendiscovered that similar multilayer adhesive constructions do not losesignificant adhesive strength on aging at room temperature for up tothree months.

                                      TABLE III                                   __________________________________________________________________________               Upper                                                                              Upper Lower                                                                              Lower                                                         Adhesive                                                                           Layer Coat                                                                          Adhesive                                                                           Layer Coat                                                                          Release                                      Facestock  Layer                                                                              Weight                                                                              Layer                                                                              Weight                                                                              Layer                                        __________________________________________________________________________    Example 1                                                                           HG   F1   15 g/m.sup.2                                                                        F2    5 g/m.sup.2                                                                        BG                                           Example 2                                                                           HG   F2    5 g/m.sup.2                                                                        F1   15 g/m.sup.2                                                                        BG                                           Example 3                                                                           HG   F2   10 g/m.sup.2                                                                        F1   10 g/m.sup.2                                                                        BG                                           Example 4                                                                           HG   F2   15 g/m.sup.2                                                                        F1    5 g/m.sup.2                                                                        BG                                           Example 5                                                                           HG   F1   20 g/m.sup.2                                                                        --   --    BG                                           Example 6                                                                           HG   F2   20 g/m.sup.2                                                                        --   --    BG                                           Example 7                                                                           Polyester                                                                          F2    5 g/m.sup.2                                                                        F1   15 g/m.sup.2                                                                        BG                                           Example 8                                                                           Polyester                                                                          F2   10 g/m.sup.2                                                                        F1   10 g/m.sup.2                                                                        BG                                           Example 9                                                                           Polyester                                                                          F2   15 g/m.sup.2                                                                        F1    5 g/m.sup.2                                                                        BG                                           Example 10                                                                          Polyester                                                                          FI   20 g/m.sup.2                                                                        --   --    BG                                           __________________________________________________________________________     HG = High Gloss white paper                                                   F1 = Formulation 1 from Table I                                               F2 = Formulation 2 from Table I                                               BG = Silicon coated 40 lb. backing paper                                      Polyester facestocks used were composed of MYLAR, manufactured by DuPont      Chemical Co. of Wilmington, Delaware                                     

                  TABLE IV                                                        ______________________________________                                                                         High Density                                 Adhesive Stainless Steel                                                                           Cardboard   Polyethylene                                 Const. from                                                                            Average Initial                                                                           Average Initial                                                                           Average Initial                              Table III                                                                              Looptack N/m                                                                              Looptack N/m                                                                              Looptack N/m                                 ______________________________________                                        Ex. 1    1090 (±110)                                                                            177 (±59)                                                                              760 (±200)                                Ex. 2     730 (±120)                                                                            224 (±50)                                                                              587 (±40)                                 Ex. 3     800 (±200)                                                                            152 (±44)                                                                              585 (±37)                                 Ex. 4     690 (±150)                                                                             75 (±9) 450 (±110)                                Ex. 5     650 (±46)                                                                             147 (±35)                                                                              420 (±120)                                Ex. 6     168 (±43)                                                                              1.8 (±16)                                                                             111 (±32)                                 Ex. 7     720 (±68)                                                                             265 (±68)                                                                              330 (±170)                                Ex. 8     776 (±26)                                                                             182 (±32)                                                                              301 (±78)                                 Ex. 9     615 (±33)                                                                             100 (±25)                                                                               98 (±33)                                 Ex. 10    648 (±21)                                                                             305 (±20)                                                                              350 (±110)                                ______________________________________                                    

The adhesive layers of the present invention may be coated ontofacestock or release liners by any means known to those of skill in theart. For example, it is contemplated that adhesive layers 24 and 26 maybe applied by solvent coating, hot melt coating, or emulsion coating, atone or more coating stations. Adhesive layers 24 and 26 might also becoated to different substrates, and then be laminated together to forman integral product. Other known methods of simultaneous coating includeslide coating, multilayer die coating, or die/slide combination coating.

One preferred method of manufacture uses a multilayer die 50 such asthat illustrated in FIG. 5. Although the die shown in FIG. 5 illustratesthe application of two coating layers to a substrate 52, it will beunderstood that the principles of this method are equally applicable toa plurality of layers in addition to two. In accordance with standardpractice, the substrate, which in this case preferably comprisessilicone coated paper, is referred to as a "web" and is formed into along roll. The web 52 travels around a back-up roll 54 as it passes thedistal end of the multilayer die 50. As shown in FIG. 5, it will beunderstood that both the die 50 and the web 52 have substantially equalwidth such that the entire width of the substrate is coated in one passby the fluid flowing out of the die 50 and onto the web 52. In thiscase, two separate fluid layers are flowing out of manifolds 56 formedin the die and along individual slots 60 which are defined by the die'sdistal lands 62. The slots 50 each communicate with the interfacebetween the web 52 and the distal most tips 58 of the die 50. These tipsare referred to as the "die lips" 58 and are illustrated and describedin more detail in connection with FIG. 6 below.

The multilayer die 50 is modular, thus allowing for variations in theindividual slots 60 and lip 58 configurations without necessitatingmodifications to the other slots and lips. Thus, these geometries can beadjusted in order to achieve successful coating. Other variables includethe "coating gap" (c.g.) and the "angle of attack" (a) of the die. Asillustrated in FIG. 5, the coating gap is the distance that the lips 58are set back from the web. The angle of attack (a) is the degree ofangular adjustment of the lip surfaces and of the entire die withrespect to the outer pointing normal of the web as illustrated in FIG.7. Another variable is the web speed which may vary between 50-1,000feet per minute, and more.

Either one of two die coating methods may be utilized: interferencecoating or proximity coating. In the former case, the lips 58 of the dieactually are pressed forward in the direction of the web 52, but do notcontact the web nor cause any damage thereto, because they hydroplane ona thin layer of coating material. However, the pressure may actuallycause the back-up roll 54 (typically constructed from a hard rubbermaterial) to deform in order to relieve the pressure of the die againstthe lips 58. In proximity coating, the lips 58 of the die 50 arepositioned a precise distance from the web 52 and are not pressedforward toward the web. The back-up roll 54 is typically constructedfrom a stainless steel material which allows for precision in thecircumference of the roll and minimizes roll run-out. The methoddescribed herein can be successfully utilized with either type ofcoating technique.

Thus, since very thin layers of high viscosity adhesives are beingcoated at relatively high web speeds, the process must be carefullycontrolled.

Such control is accomplished with the present multilayer die coatingtechnique, in part due to the geometry and configuration of the die lips58. Referring to FIG. 6, there is shown a close-up view of the distalmost tips 62 of the multilayer die of FIG. 5, including the lips 58associated with each slot, showing the interface or coating gap withrespect to the web 52. With respect to FIG. 6, it should be noted that,for ease of illustration, the die 50 is shown rotated 90° from theposition shown in FIG. 5. Moreover, the web 52 is shown in a horizontalarrangement, when in actuality, there may be a slight curvature to theweb 52 and back-up roll (not shown) at this point; however, thedistances involved are so short that a good approximation of the fluiddynamics can be achieved by assuming a horizontal web 52.

For consistent reference, the individual lips 58 of the multilayer die50 shall be referred to with respect to the direction of travel of theweb 52. For example, the lip 58a shown to the left in FIG. 6 will bereferred to as the "upstream lip," while the right-most lip 58c shall bereferred to as the "downstream lip." Thus, the "middle lip" 58b willhave that same reference. Accordingly, the upstream and middle lips 58a,58b define an upstream feed gap 64 through which an adhesive material 66flows onto the web 52 to form a bottom adhesive layer 68 of a multilayeradhesive product. Likewise, the middle lip 58b and the downstream lip58c together form a slotted feed gap 70 through which adhesive 72 flowsonto the top of the lower layer 68 as the web travels in left-to-rightdirection, as illustrated in FIG. 6. This forms a top adhesive layer 74of the multilayer adhesive product. Again, for ease of illustration, thetop layer 74 is shown as a darker-colored material, but this may notnecessarily be the case in actual production; for instance, variouscolors or tags such as ultra-violet fluorescent dye may be utilized tofacilitate measurement of individual layer thicknesses.

Coating of viscous adhesives at these web speed rates can involve anumber of problems. For example, recirculations in the flow of eitherthe bottom or top adhesive layers can result in certain defects in thefinal multilayer product. Such recirculations may occur if theseparation point of either liquid adhesive with respect to the die lips58 occurs at an inappropriate location. In addition, extreme pressuregradient can result in the upstream leakage of liquid out of the coatinggap area, again causing defects in the end product due to nonuniformadhesive layer thicknesses, etc. Moreover, these and other maleffectsresult in the diffusion of one layer in the other, since they are beingcoated simultaneously in the liquid state. Such diffusing jeopardizesthe integrity and performance of the resulting product.

Thus, it has been found, with respect to the multilayer die coatingdescribed herein, that it is very important to control the pressuregradients of the adhesives under each lip. In particular, the top layershould separate from the middle lip at the downstream corner of thislip. In order to achieve such coating control, it will be noted fromFIG. 6 that the lips 58 of each die section are stepped or spaced awayfrom the web 52 in the downstream direction. This allows the lips togenerate the appropriate pressure gradient and to ensure smooth flow ofthe adhesive and uniform layer thicknesses. The adjustment of a numberof run parameters are necessary in order to achieve this goal. Forexample, the coating gaps at lip 58b and 58c should be approximately inthe range of one to three times the compounded wet film thicknesses ofthe layers being fed from upstream of said lip. Under the upstream lip58a, the net flow rate is necessarily zero, and a turn-around flow isthe only possibility. Thus, the coating gap under this lip is solely setin order to avoid leakage of the liquid out from the coating gap in theupstream direction. Moreover, the upstream step, defined as dimension Ain FIG. 6, and the downstream step, defined as dimension B, may rangeanywhere from zero to four mils (0.0 inches to 0.004 inches). The feedgaps (defined as dimensions C and D in FIG. 6) can also be adjustedanywhere between one and fifteen mils (0.001 inches to 0.015 inches),preferably not to exceed five times the wet film thickness of theircorrespondent layers. In addition, the length of the lips 58 in thedirection of web travel play an important role in achieving the properpressure gradient. Thus, the upstream lip 58a should be approximatelytwo millimeters in length, or more, as necessary to seal the head asnoted above. The downstream lip 58c and middle lip 58b may fall withinthe range of 0.1-3 mm in length.

It will be recognized that one of ordinary skill in the art can adjustthese various parameters in order to achieve the proper fluid dynamicsfor uniform layer coating. Of course, persons of more than ordinaryskill can adjust the die and run parameters more precisely in order toachieve good results. However, such persons are not always readilyavailable in production settings. Therefore, it is advantageous toprovide a die geometry which will increase the size of the window ofsuccessful multilayer coating operation. This can be achieved by certainadjustments in the orientation of the die lips.

Thus, FIG. 7 illustrates the die 50 of FIG. 6 rotated slightly in theclockwise direction representing an "angle of attack α. For consistentreference, the angle of attack (α) shown in FIG. 7 represents a negativeangle of attack, or a "converging" orientation of the downstream lip 58cwith respect to the web 52. This converging lip orientation provides anegative pressure gradient (in the direction of web travel), along thedownstream lip 58c, which is beneficial in preventing a coating defectwell known as "ribbing," a pattern of regular striation in the sense ofthe web travel in the film. The fact that the middle and the upstreamlips 58a and 58c also achieve a convergent orientation is notparticularly beneficial. Although the angle of attack of the die can bevaried widely in order to achieve these advantages, it has been foundthat angles in the rate of 0° to -5° are appropriate.

An even further successful operating window can be achieved withadditional lip modifications. Shown in FIG. 8 is a variation of the lipconfiguration of FIG. 7, illustrating "beveled" lips. In thisconfiguration, the downstream lip 58c is angled or beveled to as to havea converging profile, similar to that shown in FIG. 7. However, themiddle lip 58b is positioned so as to be flat or parallel with respectto the web 52. The upstream lip 58a, on the other hand, is beveled sothat it is diverging from the web 52 in the downstream direction. Thisconfiguration, again, provides the appropriate pressure gradient underthe individual lips to avoid recirculations and upstream leakage.Moreover, if perturbations in the coating conditions occur (such as, forexample, due to roll run-out, foreign objects on the web, variations inambient pressure, etc.), the converging configuration of the upstreamlip 58a shown in FIG. 8 will produce a dampening effect on flowconditions so that defects in the coating layers do not occur. In thismanner, the multilayer coating bead acts as a nonlinear spring to dampenout such unwanted events in order to return to steady state. The die 50can then be adjusted in accordance with standard angle of attackvariations to achieve favorable coating conditions. Because the lips 58are pre-disposed or beveled in a favorable orientation, the adjustmentof angle of attack, as well as coating gap, need not be so precise.Thus, persons of ordinary skill or even less skill can successfullyachieve good coating results.

It will be understood, however, by those of ordinary skill in themultilayer coating art, that multilayer die coating can be achieved in avariety of ways similar to those described above, or in other ways, andwith appropriate adjustments of the various parameters for coating.

CONVERTING EXPERIMENT

To assess the converting characteristics of pressure-sensitive adhesiveconstructions of the present invention, a converting trial wasperformed.

A dual die apparatus was used to hot melt coat adhesive Formulations 1and 2, as disclosed in Table 1, on a 15" wide release liner consistingof 40 lb. silicone coated backing paper. Formulation 1 was coated on thesurface of the release liner at 10 g/m², and Formulation 2 was coated onFormulation 1 at 10 g/m². A 60# High Gloss white facestock was thenlaminated to the adhesive layer formed of Formulation 2, to form thefinal pressure-sensitive adhesive construction. This construction wasequivalent to the construction of Example 3 of Table III, having a glasstransition temperature difference between the upper and lower layers, asdisclosed in Table II, of about 23.3° C.

A control pressure-sensitive adhesive construction, similar toconventional pressure-sensitive adhesive constructions in having onlyone adhesive, was formed using Formulation 1 at a coat weight of 20g/m², using the same facestock and release liner. The laminated controlwas equivalent to the construction of Example 5 of Table III.

The control and multilayer pressure-sensitive adhesive construction werethen converted through a Mark Andy Model 1420 press utilizing an X-die(4 labels across, 15/16" label width, 3.42" label length, 3/32" radiusrounded label corner, with a 1/16" cross direction matrix and a 7/64"machine direction matrix). After the die cutting operation, the matrixsurrounding the labels was peeled away to leave rows of four rectangularlabels adhered to the release liner.

The efficacy of the converting process was monitored by the pressoperator, who observed the die cutting and matrix stripping operations.The existence of "hangers," a term used to describe an adverseconverting condition where pieces of the matrix are left on the releaseliner, were noted as a function of the press speed. Faster press speedsand an absence of hangers is indicative of a construction which convertsbetter.

For Example 3, no hangers were noted at converting speeds of up to 800feet per minute. For the control, Example 5, hangers were noted at anapproximate press speed of 650 feet per minute. Thus, the multilayerconstruction of the present invention converted at higher speeds withless adverse effects than did the conventional pressure-sensitiveadhesive construction.

A second control, consisting of Formulation 3 from Table I, was hot meltcoated as a single layer on a 40# silicone coated release layer. A 60#High Gloss white facestock was then applied. Three different coatweights, of 15 g/m², 20 g/m², and 25 g/m² were applied to form threeconstructions. These constructions were converted through a Mark Andypress, as described above. It was observed that the 15 g/m² coat weightconstruction converted at 700 feet/min, the 20 g/m² coat weightconstruction at 650 feet/min, and the 25 g/m² coat weight constructionat 315 feet/min. Thus, for the single-layer construction, rubber-basedPSA control used in these tests, converting speed was seen to decreasedramatically at coat weights over 25 g/m².

It will be appreciated that certain variations of the present inventionmay suggest themselves to those skilled in the art. The foregoingdetailed description is to be clearly understood as given by way ofillustration, the spirit and scope of this invention being limitedsolely by the appended claims.

What is claimed:
 1. A multilayer pressure-sensitive adhesiveconstruction with improved label convertibility in comparison to asingle layer adhesive construction, the multilayer adhesive constructioncomprising:a facestock; a first adhesive layer on the facestock, thefirst adhesive layer comprising a first adhesive composition with afirst glass transition temperature; a second adhesive layer on the firstadhesive layer, the second adhesive layer comprising a second adhesivecomposition with a second glass transition temperature lower than thefirst glass transition temperature; a release surface on the secondadhesive layer; and wherein the first and the second layers when appliedhave a combined specified thickness, and the multilayer adhesiveconstruction so formed is capable of being converted to a labelconstruction by a press utilizing a die-cutting and matrix strippingoperation without formation of hangers at a rate in feet per minutewhich is substantially greater than that of a comparison adhesiveconstruction comprising a single layer of the second adhesivecomposition applied in an amount such that the single layer has aboutthe specified thickness.
 2. The multilayer pressure-sensitive adhesiveconstruction of claim 1, wherein the first glass transition temperatureis within the range of from about 10° C. to about 50° C. higher than thesecond glass transition temperature.
 3. The multilayerpressure-sensitive adhesive construction of claim 2, wherein the firstglass transition temperature is within the range of from about 15° C. toabout 35° C. higher than the second glass transition temperature.
 4. Themultilayer pressure-sensitive adhesive construction of claim 1, whereinthe multilayer adhesive construction is capable of being converted to alabel construction at a rate of at least 650 feet per minute.
 5. Themultilayer pressure-sensitive adhesive construction of claim 1, whereinthe multilayer adhesive construction is capable of being converted to alabel construction at a rate of at least 800 feet per minute.
 6. Themultilayer pressure-sensitive adhesive construction of claim 3, whereinthe first layer has a storage modulus at a frequency of 10⁴ radians/secat 20° C. which is greater than about 3×10⁸ dynes/cm.
 7. The multilayerpressure-sensitive adhesive label construction of claim 1, wherein atleast one of the first or second adhesive compositions comprises anelastomeric polymer having at least one organic additive.
 8. Themultilayer pressure-sensitive adhesive label construction of claim 1,wherein at least one of the first or second adhesive compositionscomprises an acrylic-based polymer or copolymer.
 9. The multilayerpressure-sensitive adhesive construction of claim 1, wherein the firstadhesive composition comprises a first elastomeric polymer and has atleast a first organic additive, and the second adhesive compositioncomprises a second elastomeric polymer and has at least a second organicadditive.
 10. The multilayer pressure-sensitive adhesive construction ofclaim 9, wherein at least one of the first and second elastomericpolymers is selected from the group consisting of block copolymers ofstyrene-butadiene-styrene, styrene-isoprene-styrene, styrene-butadiene,styrene-isoprene, multibranched styrene-butadiene, and multibranchedstyrene-isoprene.
 11. The multilayer pressure-sensitive adhesiveconstruction of claim 9, wherein at least one of the first and secondelastomeric polymers is a blend of two or more block copolymers selectedfrom the group consisting of styrene-butadiene-styrene,styrene-isoprene-styrene, styrene-butadiene, styrene-isoprene,multibranched styrene-butadiene, and multibranched styrene-isoprene. 12.The multilayer pressure-sensitive adhesive construction of claim 9,wherein at least one of the first organic additive and the secondorganic additive includes at least one tackifier present in aconcentration by weight in the respective first and second adhesivecompositions of from about 40% to about 90%.
 13. The multilayerpressure-sensitive adhesive construction of claim 12, wherein at leastone of the first and second organic additives further includes aplasticizer present in a concentration by weight of about 1% to about30%.
 14. The multilayer pressure-sensitive adhesive construction ofclaim 12, wherein the ratio of the first elastomeric polymer to thefirst organic additive divided by the ratio of the second elastomericpolymer to the second organic additive is between about 0.8 and about1.2.
 15. A multilayer pressure-sensitive adhesive label construction,comprising:a facestock; a first adhesive layer on the facestock, thefirst adhesive layer having a first coat weight; a second adhesive layeron the first adhesive layer, the second adhesive layer having a secondcoat weight; and wherein the combined coat weight of the first andsecond adhesive layers is no greater than about 30 g/m² and the adhesivelabel construction is formed from a laminate construction capable ofbeing converted to a label construction by a die-cutting and matrixstripping operation performed by a 15 inch-wide press which utilizes adie with a 1/16th inch cross-directional matrix and converts at a rategreater than 315 feet per minute without formation of hangers.
 16. Themultilayer pressure-sensitive adhesive label construction of claim 15,wherein the first adhesive layer comprises a first adhesive compositionwith a first glass transition temperature, and the second adhesive layercomprises a second adhesive composition with a second glass transitiontemperature, and the first glass transition temperature exceeds thesecond glass transition temperature by an amount within the range offrom about 10° C. to about 50° C.
 17. The multilayer pressure-sensitiveadhesive label construction of claim 16, wherein at least one of thefirst and second adhesive compositions comprises an acrylic-basedpolymer.
 18. The pressure-sensitive adhesive construction of claim 17,wherein the acrylic-based polymer is formed in part from thepolymerization of at least one alkyl acrylate monomer containing fromabout 4 to about 12 carbon atoms in the alkyl group, and present in anamount from about 35% to about 95% by weight of the polymer.
 19. Themultilayer pressure-sensitive adhesive label construction of claim 9,wherein one or more additional layers are positioned between the firstadhesive layer and the second adhesive layer.
 20. The multilayerpressure-sensitive adhesive label construction of claim 15, furthercomprising at least a third adhesive layer positioned between the firstadhesive layer and the second adhesive layer.
 21. The multilayerpressure-sensitive adhesive label construction of claim 15, wherein theconverting press is a Mark Andy press which utilizes an X-die.
 22. Themultilayer pressure-sensitive adhesive label construction of claim 21,wherein the facestock is formed from 60 lb. High Gloss paper.
 23. Themultilayer pressure-sensitive adhesive label construction of claim 15,wherein the multilayer adhesive construction is capable of beingconverted to a label construction at a rate of at least 650 feet perminute.
 24. The multilayer pressure-sensitive adhesive labelconstruction of claim 15, wherein the adhesive construction is capableof being converted to a label construction at a rate of at least 800feet per minute.
 25. A multilayer pressure-sensitive adhesiveconstruction, comprising:a facestock; a first layer on the facestock,the first layer comprising a first polymeric composition with a firstglass transition temperature, a first storage modulus at a frequency of10⁴ radians per second at 20° C. which is greater than about 3×10⁸dynes/cm², and a first tangent delta; a second layer on the first layer,the second layer having a second polymeric composition with a secondglass transition temperature, wherein the second polymeric compositionis also a pressure-sensitive adhesive; and wherein the adhesiveconstruction is capable of undergoing a die-cutting and matrix strippingconversion process on a 15 inch-wide press which utilizes a die with a1/16th inch cross-directional matrix to form a label construction atpress speeds in excess of 315 feet per minute without formation ofhangers.
 26. The pressure-sensitive adhesive construction of claim 25,where the first tangent delta at 20° C. and 10² radians per second isgreater than 0.5.